HIGH-YIELD SYNTHESES OF SODIUM, POTASSIUM, AND THALLIUM HYDROTRIS[3,5-BIS(TRIFLUOROMETHYL)PYRAZOLYL]BORATES AND THE X-RAY CRYSTAL-STRUCTURE OF(HYDROTRIS[3,5-BIS(TRIFLUOROMETHYL)PYRAZOLYL]BORATO)THALLIUM(I)

An improved synthesis of 3,5-bis(trifluoromethyl)pyrazole (1) is described. This compound was used for the high-yield syntheses of the tris(pyrazolyl)borates Na[HB(3,5-(CF3)(2)-pz)(3)] (2a) and the corresponding potassium salt, 2b, starting from 1 and NaBH4 and KBH4, respectively. A convenient route to the corresponding thallium(I) salt, 2c, using thallium(I) acetate and either 2a or 2b in CHCl3, is also described. The sodium (3a), potasium (3b), and thallium (3c) salts of bis(pyrazolyl)borate [H2B(3,5-(CF3)(2)-pz)(2)](-) were also prepared. The above pyrazolylborates were characterized by H-1-, C-13-, F-19-, and B-11-NMR spectroscopy. The X-ray crystal structure of the thallium derivative 2c was determined. The compound crystallizes in the monoclinic space group P2(1)/m with a = 8.248(9) Angstrom, b = 15.034(12) Angstrom, c = 9.243(8) Angstrom, beta = 100.10(7)degrees, Z = 2. The Tl-atom adopts a pyramidal geometry with respect to the three N-atoms. However, two Tl-N distances (2.725(7) Angstrom) are longer than the third (2.675(10) Angstrom).